1. Field of the Invention
The present invention relates to a thin provisioning technology for a storage system and a computer system.
2. Description of the Related Art
With the wide use of a computer, the size of data for handling has been increasing with each passing year. A storage device serves to store such a large-size data with safety and efficiency, and provides a volume (data container) through connection with a computer over a communications line. The problem is that, however, the volume cannot be basically changed dynamically in capacity in accordance with the state of use. This thus requires the volume capacity to be allocated adequately to be on the safe side at the time of system construction, thereby failing to use the capacity resources with good efficiency.
On the other hand, with the thin provisioning technology, a host is provided with a volume having a virtual capacity, i.e., virtual VOL, and on the end of a storage, the capacity is allocated only to data actually written, thereby being able to utilize the volume capacity with good efficiency. A writing destination of data is a large-capacity boundary-free pool configured by a plurality of volumes. Such volumes are hereinafter referred to as pool volumes: “Pool VOLs”. As such, the virtual VOL is provided by the pool, the pool is by the Pool VOL, and the Pool VOL is by a physical device (array group). With such a configuration, when a blockage occurs due to a failure of any of the lower components, the components upper thereto basically become entirely not available for use.
In consideration thereof, Patent Document 1 (JP-2006-338341) describes the technology of specifying and correctly blocking, at the time of component blockage, any related portion of blockage by storing the configuration of the components for thin provisioning.
The storage device has been essential infrastructure for continuous business operations mainly for corporations handling a large amount of data. If volumes and data are corrupted and become not available for use due to unexpected accidents and disasters, and computer virus and application error, for example, the business operations may be seriously affected. To be ready for such unexpected volume and data corruption, the data is generally replicated using a copy control function provided by the storage. The result of data replication is referred to as replica or backup. Such data replication in the same storage is hereinafter referred to as local copy, and data replication between the storages is referred to as remote copy. With the copy control function, data synchronization is established from a primary volume (P-VOL) to a secondary volume (secondary VOL). A pair of primary and secondary volumes is referred to as copy pair, and the copy pair is in two states of Pair (synchronous) state and Suspend state. In the Pair state, data is always synchronous, and in the Suspend state, data is not synchronous. Using the copy control function, the state of the copy pair can be changed from the Pair state to the Suspend state, i.e., Split, and from the Suspend state to the Pair state, i.e., Resync. When a logical failure occurs to data in a primary volume, for example, data restoring (Restore/Reverse Resync) can restore the data in the primary volume to the data stored in a secondary volume.
When a replica of a virtual volume is created with the thin provision technology described above, the virtual capacity of the primary volume being a copy source has to be saved as the substantial capacity on the secondary volume end, thereby failing to use the storage capacity of the storage with good efficiency.
In consideration thereof, Patent Document 2 (JP-A-2007-133822) describes the technology of copying, from a copy source, with a secondary volume being a virtual volume, only any data using the real capacity, i.e., only data being allocated with the real storage area, through application of the thin provisioning function also in a copy destination.
In view of efficient use of the storage capacity, there is an external connection function of increasing the volume capacity of the storage device by mapping, into the storage device, a volume (external VOL) of an external storage device (external storage). With such an external connection function, similarly to any internal volume, the internally-mapped external VOL is basically applicable with resources and functions originally provided to the storage device.